The prior art is replete with systems in which multiple valves are assembled by way of being housed in individual, modular, units which are adapted to be plugged together so that a system can be created. Typically, each individual valve is housed in a valve housing unit in which both hydraulic and electrical passages are formed to selectively provide the electrical signals to actuate--typically through a solenoid--a particular one or more of the several valves. The necessary electrical interconnections to connect together a plurality of the individual valve housings has typically been accomplished by individually hand wiring each valve housing to its adjacent cousins so that a common control system can be utilized. Such hand wiring is difficult and time consuming and results in increased manufacturing costs.
More recent modular valve systems eliminate the hand wiring by providing each pluggable valve housing unit with pre-printed circuit boards so as to eliminate the tedious and inefficient hand wiring process to thereby create a more modular system. However, such systems are compromised electrically because both the control and the actuating signals required for each valve are furnished in a common electrical circuit having one power supply massive enough to supply the power, typically 24 volts, required to drive a solenoid which opens or closes a particular valve in the system. Such a massive power supply is of course completely unnecessary for driving the circuits which produce the control signals which, themselves, really need no more power than required for typical control signals which can be generated with power supplies as low as 3 to 5 volts, for example, those control signals generated by a small computer.
When both the control and actuation signals are provided by a single, common power supply, in a common circuit with a common ground, undesirable transient and crosstalk effects can arise to interact and create electronic noise effecting either the control signals or the valve actuation signals and result in undesirable interference between.
Accordingly, it a primary object of this invention to eliminate the above-noted problems in the prior art and to provide a system which eliminates both the expensive and time consuming manual hand wiring as well as the undesirable cross talk between the control and actuation signals.